Thallium Valence Electrons (And How to Find them?)

So you have seen the above image by now, right?

Awesome! You can see that thallium has 3 valence electrons.

But how can you say that Thallium has 3 valence electrons
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How can you find these valence electrons?

Let’s discuss this in short.

Thallium has 3 valence electrons because there are 3 electrons present in the outermost shell of the Thallium (Tl) atom.

Now let’s see how you can easily find the valence electrons of Thallium atom (Tl).

You can also refer to this video for finding the valence electrons of any elements.

How to find the Valence Electrons? (2 Methods)

In order to find the valence electrons of a Thallium atom (Tl), you can use two methods.

Method 1: From the Periodic Table

To find out the valence electrons of Thallium, you have to see the position of thallium in the periodic table.

More specifically, you have to see the group wise position of Thallium element in the periodic table.

From the above image, you can see that the Thallium (Tl) is present in the group 13 of periodic table.
(Note: Group 13 is also called group 3A).

So, as the thallium element is present in group 13, it has 3 valence electrons.

In this way, by knowing the position of thallium element in periodic table, you can easily find its valence electrons.

Now let’s see another method for finding the number of valence electrons in thallium.

Method 2: From the Electron Configuration

If you want to find the valence electrons of thallium from its electron configuration, then you should know its electron configuration first.

Now there are many methods to write the electron configurations, but here I will show you the easiest method, i.e by using Aufbau principle.

Aufbau principle: The Aufbau principle simply states that the orbitals with the lower energy are filled first and then the orbitals with higher energy levels are filled.

According to the Aufbau principle, the orbitals are filled in the following order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, and so on.

Also the maximum number of electrons that can be accommodated in s, p, d & f orbitals are mentioned in the below table.

Now let’s try to find the electron configuration of Thallium by using the Aufbau principle.

Electron Configuration of Thallium:

Follow the steps mentioned below to get the electron configuration of Thallium.

• To write the electron configuration of thallium, we should first know the total number of electrons present in a thallium atom.
• The thallium atom has a total of 81 electrons because its atomic number is 81 and it is a neutral atom[2]
• Now we have to fill these 81 electrons in the atomic orbitals according to the Aufbau principle.
• According to the Aufbau principle, the electrons will be filled first in 1s orbital, then in 2s orbital, then in 2p orbital, and so on…
• So from the Aufbau principle, we can get the electron configuration of the thallium atom as 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p1. [3]

Now in this electron configuration of thallium, we have to see the total number of electrons present in the highest energy level.

You can see in the electron configuration of thallium (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p1) that the highest energy level is 6. And the total number of electrons present in this energy level is 2 + 1 = 3.

So by knowing the electron configuration, we have found that the Thallium has 3 valence electrons.

I hope you have understood the methods of finding the valence electrons in thallium.

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